Along-strike variation of the frontal zone structural geometry of the Central Longmen Shan thrust belt revealed by seismic reflection profiles

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• 作者：Renqi Lu^a ; ^c ; ^{lurenqi@163.com} ; Dengfa He^b ; John Suppe^c ; Yongsheng Ma^d ; Bo Liu^a ; Yuegau Chen^c
• 关键词：Seismic interpretation ; Surface ruptures ; Co-seismic fault ; Pengguan fault ; 3-D fault geometry ; Longmen Shan
• 刊名：Tectonophysics
• 出版年：2012
• 出版时间：10 December, 2012
• 年：2012
• 卷：580
• 期：Complete
• 页码：178-191
• 全文大小：6102 K

文摘

The 2008 Ms 8.0 Wenchuan earthquake of China ruptured two large faults along the Beichuan-Yingxiu thrust belt and the Pengguan thrust belt at the Longmen Shan Orogenic belt, eastern margin of the Tibetan Plateau. Our study focused on the structural geometry at the Pengguan thrust belt located at the frontal zone of the Central Longmen Shan. In this paper, in order to identify the co-seismic fault at the Pengguan thrust belt many 2-D/3-D seismic reflection profiles have been interpreted by integrating with the geological maps, drilling data, DEM data and the surface ruptures. The results show that there were three major faults and other branch faults at the Pengguan thrust belt. The major faults have formed as imbricates and associated minor duplexes within the shallow strata. The Pengguan fault has a steep dip at the shallow surface and a gentle dip at depth. Both the Beichuan-Yingxiu fault and the Pengguan fault were developed on the shallow detachment in the central segment of Longmen Shan. The third (No. ¢Û) Pengguan fault is coincident with the co-seismic surface ruptures. It was a pre-existing fault and re-activated during the Wenchuan earthquake. Three-dimensional geometries show that the No. ¢Û fault is heterogeneous and it has controlled the slip of co-seismic ruptures. Based on the regional geology, the 3-D fault geometry and the surface ruptures, the frontal zone of the Central Longmen Shan has been divided into the Bailu segment and the Hanwang segment. Our studies suggest that the Pengguan fault has been active since the Cenozoic. The frontal zone of the Central Longmen Shan thrust belt has potential for future earthquakes.